Pneumatic actuated switches are used in applications where it is desirable to actuate an electrical component at a remote location by means of a pulse of air. Such switches typically have a diaphragm assembly disposed adjacent to an electrical switch. The diaphragm assembly includes a resilient diaphragm element disposed adjacent a pressure chamber. The diaphragm element is designed to move and activate the switch in response to a pressure increase in the pressure chamber. In general, the pressure chamber is connected by a circuit or channel, typically tubing, to a remote actuator or pressure source. The actuator and circuit or channel leading up to the pressure chamber are air tight to ensure transfer of a pressure pulse from the actuator or pressure source into the pressure chamber.
Such switches are often utilized in applications where the switch and actuator are exposed to elevated temperatures (e.g., furnace, hot tub, spa, jetted bathtub applications or the like). A problem with using such switches in these types of environments is that air confined within the pressure chamber, or the channel or circuit communicating with the actuator, may at elevated temperatures expand sufficiently to cause movement of the diaphragm element and unintentional activate the electric switch. To overcome this problem, some pneumatic actuated switches include a sintered metal disk, bleeder or like device which allow a slow release of pressure from the pressure chamber. The addition of these components in the pressure chamber, however, limits the type of electric switch which can be used with the pneumatic actuator. In this respect, a pressure increase applied to the diaphragm cannot be maintained for a prolonged period of time because the sintered disk or bleeder element allows a gradual release of pressure in the pressure chamber. Consequently, such arrangements are typically limited to use with "alternate action" switches, as compared to "dwell" or "momentary" switches. In this respect, "alternate action" switches activate instantaneously and typically require successive pressure pulses to move the diaphragm twice to cause an "on" and "off" cycle. On the other hand, "dwell" or "momentary" type switches remain "on" only so long as the switch's actuator is depressed. Release of the force on the actuator allows the switch to return to "off." In addition to the foregoing, the addition of sintered discs and bleeders to a pneumatic actuated switch increases the overall manufacturing cost of the switch.
The present invention overcomes these and other problems and provides a diaphragm assembly for use in a pneumatic actuated switching device, which diaphragm assembly is sensitive to the rate of pressure change exerted thereon. The diaphragm assembly is operable to allow gradual pressure release until the rate of pressure increase exerted thereon reaches a predetermined level sufficient to cause the diaphragm to move from a neutral unflexed position to a flexed condition, thereafter, further venting of pressure from the pressure chamber is prevented.